Molding mixture



Patented July 23, 1929.

'IZUNITED STATES? PATENT. OFFICE.

CLARENCE .A. NASH, OF NEWARK, NEW JERSEY ASSIGNOR TO BAKELITE CORPORA- TION, F YORK, N. Y., A CORPORATION OE DELAWARE.

MOLDING MIXTURE.

' 1T0 Drawing.

This invention is a novel molding mixturepreferably prepared by reacting urea and formaldehyde or their equivalents, in presence of filling materials including cellulose 5 esters.

It is well known that urea and formaldehyde are capable of reacting to yield clear resins which become infusible when ,sufiicient- 1y heated; but the resins thus prepared do not function satisfactorily asbinders for the usual fibrous or other fillers such as are'eommonly used in conjunction with reactive resins ofthe phenol-aldehyde type. I have found however that by suflicient additions of cellulose esters, properly incorporated into the resin, this defect may be overcome. The

molded products made from these novel mix tures by the standard procedures of hot-press molding are moreover superior iii-their sur- 2 face characteristics and in their resistance to moisture. I prefer to use cellulose acetate, although the lower nitrates (corresponding to the .di-nitro compounds) may be satisfactorily employed. Higher nitration products which are unstable at the molding tempera- .tures of the order of 165 C. or somewhat higher are to be avoided. I

The present invention is not limited to any specific composition of moldingmixture or to any particular method of securing the necessary intimate incorporation of the cellulose ester into the resin. Preferably however the urea-formaldehyde resin is synthesized in presence of the cellulose ester, as well as of such inert fillers asmay be employed. I prefer to proceed as follows A mixture is prepared comprising by weight: 4

. Parts. Urea Paraform Cellulose'acetate: E 32 Wood flour 100 The above ingredients are thoroughly oommingled in a ball mill or other mechanical mixing device, and then transferred to mixing rolls of the differential type and sheeted.

Application filed December 1, 1926. Serial No. 152,065.

The reaction whereby the resin is formed takes place largely or entirely-during this sheeting operation, which is continued until the reaction is complete, as indicated by a loss of weight corresponding substantially .to the water which is a by-product of this reaction. The sheets are brokenup' and pulverized in accordance with standard practice. Theresulting powder may be molded under substantially the same hot-press conditions as are standard in the art of molding mixtures containing resins of the phenol-aldehyde type.

Additional plasticity may be'imparted to these molding mixtures by introducing suitable plasticizing additions into the original mixture. Among such additions I prefer to use ethylene glycol, naphthalene, the di-alkyl esters of oxalic, tartaric or phthalic acids, and the like.

'Instead of urea/I may use thiourea or in general such homologs or derivatives of urea;

as are equivalent thereto for the purposes of this invention, and the term urea is used herein to include such equivalents. I claim:

1. A molding mixture comprising a resin of the urea-formaldehyde type, a filling materiaL and a cellulose esterwhich is stable at temperatures below 165 C. a

2. A molding mixture'comprising a resin of the urea-formaldehyde type, a filling material, a cellulose ester stable at temperatures below, 165 C., and a plasticizing agent.

3. A molding mixture comprising a resin of the urea-formaldehyde type, a filling mav terial, a cellulose ester stable at temperatures below 165C., and a plasticizl ng agent including a di-alkyl ester of an organic, acid.

4. A. molding mixture comprising a resin of the urea-formaldehyde type, a filling material, and .cellulose acetate."

5. A molding mixture comprising a resl of the urea-formaldehydetype, a filling material, cellulose acetate, and aplasticizing agent.

In testimony whereof, I alfix my signature.

OLABENCEA. NASH. 

